Colorimetric value calculating method, profile generating method, color conversion method, color conversion apparatus, and computer-readable recording medium with color conversion program recorded therein

ABSTRACT

First spectral data (spectral transmittance) of a printed object, and second spectral data (spectral reflectance) of the printed object are obtained. Further, third spectral data (spectral radiance distribution) of a transmissive light source, and fourth spectral data (spectral radiance distribution) of a reflective light source are obtained. Then, using the first, second, third and fourth spectral data, colorimetric value data of the printed object in a given observational environment is calculated.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2009-212225 filed on Sep. 14, 2009, ofwhich the contents are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a colorimetric value calculatingmethod, a profile generating method, a color conversion method, a colorconversion apparatus, and a computer-readable recording medium having acolor conversion program recorded therein, in which, in an observationalenvironment where both transmissive and reflective light sourcescoexist, colorimetric values of a print made up of an image formed on alight-transmissive medium are calculated.

2. Description of the Related Art

With significant advances in inkjet technology in recent years, it hasbeen become possible for inkjet printers to produce large color printsof high quality at high speeds. Inkjet printers are not only popular forprivate or home use, but also are widely used in commercial applicationsnowadays. Inkjet printers enable prints to be made on POP (Point OfPurchase) posters, wall posters, large-size mediums such as outdooradvertisements and billboards, roll mediums, and thick hard mediums.

There are a wide variety of print mediums (hereinafter also referred toas “mediums”) available for use in prints in order to meet variouscommercial demands. For example, such print mediums include papermediums including synthetic paper, thick paper, aluminum-evaporatedpaper, etc., resin mediums made of vinyl chloride, PET, etc., andtarpaulin paper made of a woven fiber cloth with synthetic resin filmsapplied to both surfaces thereof.

Since advertisement prints are expected to be effective in arousingconsumers' motivation to buy advertised products through visualsensation, the finish of colors of the prints (printed mediums) is ofparticular importance. Heretofore, there have been disclosed variouscolor matching technologies, such as a method of generating an ICC(International Color Consortium) profile, a method of adjusting adesignated color, etc., as print color managing means.

Advertisement prints are displayed in a variety of places includingoutdoor areas, indoor areas, and spotlighted exhibition sites.Generally, the spectral characteristics (spectral energy distribution)of environmental light as an observational light source for prints varydepending on different places where the prints are displayed. As aresult, in cases where the observational light sources differ, eventhough the same print is viewed, the spectral characteristics of lightthat ultimately reaches the retinal wall of eyes of the observer aredifferent, and therefore, the appearance of the print (impression ofcolors) to the observer is subject to variation, although the tendencymay differ from observer to observer. As a consequence, if theobservational environment in which a print is produced (i.e., thelocation where the printer is installed) and the observationalenvironment in which the print is displayed differ greatly from eachother, then the print may possibly fail to exhibit desired colors.

As one method for solving such problems, Japanese Laid-Open PatentPublication No. 2007-081586 discloses a method and apparatus for storingindependently spectral data of a print, and a plurality of light sourcespectral data. A profile appropriate for an observational light sourceis generated each time that the observational light source is set up.This publication states that the method and apparatus can generateprofiles corresponding to respective different observational lightsources for colorimetric measurement in a reduced number of man-hours,and can perform appropriate color management for prints depending onsuch observational light sources.

Further, in Japanese Laid-Open Patent Publication No. 2003-298854, asspectral data which is used when a profile is generated, in place of thespectral reflectance of the print, it is disclosed that the spectraltransmittance of a film or the like can be used. (Refer to paragraph[0070] in the specification of Japanese Laid-Open Patent Publication No.2003-298854.)

However, with a print consisting of an image formed on alight-transmissive medium, in the case of an observational environmentin which both transmissive and reflective light sources coexist, orstated otherwise, in the event the print is displayed under theinfluence of both a transmissive light source and a reflective lightsource, problems occur in that colors of the print cannot be managedappropriately.

Moreover, the method and apparatus disclosed in Japanese Laid-OpenPatent Publication No. 2007-081586 and Japanese Laid-Open PatentPublication No. 2003-298854 provide no consideration for a situationwhere an observational environment is provided in which bothtransmissive and reflective light sources coexist.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a colorimetric valuecalculating method, a profile generating method, and a color conversionmethod, together with an apparatus and program therefor, which enablecolor management to be carried out appropriately for a print that isobserved under the influence of both transmissive and reflective lightsources.

The present invention concerns a colorimetric value calculating methodfor calculating a colorimetric value of a printed object including animage formed on a light-transmissive medium in an observationalenvironment in which both a transmissive light source and a reflectivelight source coexist.

The above colorimetric value calculating method comprises a firstacquisition step for acquiring a spectral transmittance of the printedobject and a spectral reflectance of the printed object, a secondacquisition step for acquiring a spectral distribution of thetransmissive light source and a spectral distribution of the reflectivelight source, and a calculating step for calculating a colorimetricvalue of the printed object in the observational environment, using theobtained spectral transmittance of the printed object, the obtainedspectral reflectance of the printed object, the obtained spectraldistribution of the transmissive light source, and the obtained spectraldistribution of the reflective light source.

Because it is configured in this manner, the aforementioned method iscapable of generating an appropriate profile of the printed object whenobserved under the influence of both the transmissive light source andthe reflective light source, whereby appropriate color managementthereof can be carried out.

Further, preferably, the method further comprises a third acquisitionstep for acquiring a degree of influence of the transmissive lightsource and the reflective light source with respect to how the printedobject is viewed, and the calculating step calculates the colorimetricvalue of the printed object in the observational environment furtherusing the degree of influence.

The colorimetric value calculating method preferably further comprisesan estimating step of estimating an optical material characteristicvalue of a protective film, a third acquiring step of acquiring aspectral transmittance of the protective film, a first predicting stepof predicting a spectral transmittance of a protective-film-coveredprint, which is made up of the printed object covered by the protectivefilm, using the spectral transmittance of the printed object and theobtained spectral transmittance of the protective film, and a secondpredicting step of predicting a spectral reflectance of theprotective-film-covered print using the spectral reflectance of theprinted object and the estimated optical material characteristic valueof the protective film. In this case, the calculating step calculates acolorimetric value of the protective-film-covered print in theobservational environment.

Further, preferably, the first acquisition step is performed using ameasuring unit for measuring the light sources, or an acquiring unit foracquiring data from a database.

Further, preferably, the third acquisition step is performed using anacquiring unit for acquiring the degree of influence based on a settingby a user, or by using an acquiring means for acquiring the degree ofinfluence by measuring the transmissive light source and the reflectivelight source.

The colorimetric value calculating method preferably further comprisesan estimating step of estimating an optical material characteristicvalue of a protective film, a fourth acquiring step of acquiring aspectral transmittance of the protective film, a first predicting stepof predicting a spectral transmittance of a protective-film-coveredprint, which is made up of the printed object covered by the protectivefilm, using the spectral transmittance of the printed object and theobtained spectral transmittance of the protective film, and a secondpredicting step of predicting a spectral reflectance of theprotective-film-covered print, using the spectral reflectance of theprinted object and the estimated optical material characteristic valueof the protective film. In this case, the calculating step calculates acolorimetric value of the protective-film-covered print in theobservational environment.

The profile generating method according to the present inventioncomprises a first acquisition step of acquiring a spectral transmittanceof a color chart serving as a printed object formed on alight-transmissive medium, a second acquisition step for acquiring aspectral distribution of a transmissive light source and a spectraldistribution of a reflective light source, which act as observationallight sources for the printed object, a calculating step for calculatinga colorimetric value of the color chart in an observational environmentin which the transmissive light source and the reflective light sourcecoexist, using the obtained spectral transmittance of the color chart,the obtained spectral reflectance of the color chart, the obtainedspectral distribution of the transmissive light source, and the obtainedspectral distribution of the reflective light source, and a generatingstep of generating a print profile based on the calculated colorimetricvalue of the color chart.

The color conversion method according to the present invention comprisesa first acquisition step of acquiring a spectral transmittance and aspectral reflectance of a color chart serving as a printed object formedon a light-transmissive medium, a second acquisition step of acquiring aspectral distribution of a transmissive light source and a spectraldistribution of a reflective light source, which act as observationallight sources for the printed object, a calculating step for calculatinga colorimetric value of the color chart in an observational environmentin which the transmissive light source and the reflective light sourcecoexist, using the obtained spectral transmittance of the color chart,the obtained spectral reflectance of the color chart, the obtainedspectral distribution of the transmissive light source, and the obtainedspectral distribution of the reflective light source, a generating stepof generating a print profile based on the calculated colorimetric valueof the color chart, and a color converting step of color convertingimage data showing an image to be printed, while using an arbitraryprofile as an input profile and using the print profile generated by thegenerating step as an output profile.

Preferably, the color conversion method further comprises an input stepof further color converting the color converted image data and supplyingthe same to a color calibration apparatus, while using the print profileas an input profile and using a profile of the color calibrationapparatus as an output profile, and an adjusting step of adjusting adegree of influence of the transmissive light source and the reflectivelight source with respect to how the printed object is viewed, whilereferring to the image output from the color calibration apparatus.

The present invention also concerns a color conversion apparatus forperforming color conversion on a printed object including an imageformed on a light-transmissive medium in an observational environment inwhich both a transmissive light source and a reflective light sourcecoexist.

The above color conversion apparatus comprises a first acquisition unitfor acquiring a spectral transmittance of the printed object and aspectral reflectance of the printed object, a second acquisition unitfor acquiring a spectral distribution of the transmissive light sourceand a spectral distribution of the reflective light source, acalculating unit for calculating a colorimetric value of the printedobject in the observational environment, using the spectraltransmittance of the printed object and the spectral reflectance of theprinted object obtained from the first acquisition unit, together withthe spectral distribution of the transmissive light source and thespectral distribution of the reflective light source obtained from thesecond acquisition unit, a profile generating unit for generating aprint profile based on the colorimetric value of the printed object inthe observational environment as calculated by the calculating unit, anda color converter for color converting image data showing the image tobe printed, while using an arbitrary profile as an input profile, andusing the print profile generated by the profile generating unit as anoutput profile.

In a computer-readable recording medium according to the presentinvention, which records therein a color conversion program for enablinga computer to carry out color conversion on a printed object includingan image formed on a light-transmissive medium in an observationalenvironment in which both a transmissive light source and a reflectivelight source coexist, the program further enables the computer tofunction as means for acquiring a spectral transmittance of the printedobject and a spectral reflectance of the printed object, means foracquiring a spectral distribution of the transmissive light source and aspectral distribution of the reflective light source, means forcalculating a colorimetric value of the printed object in theobservational environment, using the spectral transmittance of theprinted object, the spectral reflectance of the printed object, thespectral distribution of the transmissive light source, and the spectraldistribution of the reflective light source, means for generating aprint profile based on the calculated colorimetric value of the printedobject in the observational environment, and means for color convertingimage data to be displayed in an image to be printed, while using anarbitrary profile as an input profile, and using the generated printprofile as an output profile.

In accordance with the colorimetric value calculating method, theprofile generating method, the color conversion method, the colorconversion apparatus, and the computer-readable recording medium havingthe color conversion program recorded therein of the present invention,a spectral transmittance of the printed object and a spectralreflectance of the printed object are obtained, and in addition, aspectral distribution of the transmissive light source and a spectraldistribution of the reflective light source are obtained, whereupon acolorimetric value of the printed object is calculated under a givenobservational environment utilizing the spectral transmittance of theprinted object, the spectral reflectance of the printed object, thespectral distribution of the transmissive light source, and the spectraldistribution of the reflective light source. Therefore, the invention iscapable of generating an appropriate profile for the printed object,which is to be viewed under the influence of both a transmissive lightsource and a reflective light source, and whereby color management canbe carried out appropriately for the printed object.

The above and other objects, features, and advantages of the presentinvention will become more apparent from the following description whentaken in conjunction with the accompanying drawings in which preferredembodiments of the present invention are shown by way of illustrativeexample.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a printing system incorporating a colorconversion apparatus according to an embodiment of the presentinvention;

FIG. 2 is a front elevational view of a color chart according to thepresent embodiment;

FIG. 3 is a functional block diagram of an image processing apparatusaccording to the present embodiment;

FIG. 4 is a functional block diagram of an output profile managing unitaccording to the present embodiment;

FIGS. 5A through 5D are views showing by way of example setting screensfor setting profile generating conditions according to the presentembodiment;

FIG. 6 is a view showing by way of example a setting screen for settingprofile generating conditions according to the present embodiment;

FIG. 7 is a flowchart of a sequence for obtaining an appropriate colorprint using the printing system according to the present embodiment;

FIG. 8 is a flowchart of a profile generating method according to thepresent embodiment;

FIG. 9A is a perspective view for explaining a method used to measurethe luminance of a transmissive light source;

FIG. 9B is a perspective view for explaining a method used to measurethe luminance of a reflective light source;

FIG. 10 is an outline view in cross section of a measurement specimenmade for the purpose of estimating optical material property values of aprotective film;

FIG. 11 is a detailed functional block diagram of a color converter inwhich changes in spectral sensitivity distribution are taken intoconsideration; and

FIG. 12 is a perspective explanatory view of a print color calibrationsystem in which a color calibration apparatus according to the presentinvention is incorporated.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A colorimetric value calculating method, a profile generating method,and a color conversion method according to a first embodiment of thepresent invention, in relation to a color conversion apparatus and aprinting system that carry out the same, will be described in detailbelow with reference to the accompanying drawings.

FIG. 1 shows in perspective a printing system 10 incorporating an imageprocessing apparatus 16 as a color conversion apparatus according to anembodiment of the present invention.

As shown in FIG. 1, the printing system 10 basically comprises a LAN 12,an editing apparatus 14, the image processing apparatus 16 serving as acolorimetric value calculating apparatus, a printing machine 18, and acolorimeter 20 serving as a first acquisition unit.

The LAN 12 is a network constructed according to communication standardssuch as Ethernet (registered trademark) or the like. The editingapparatus 14, the image processing apparatus 16, and a database DB areconnected to each other over the LAN 12 by a wired or wireless link.

The editing apparatus 14 is capable of editing an arrangement of colorimages made up of characters, figures, pictures, photos, etc., on eachof pages to be printed. The editing apparatus 14 generates electronicmanuscripts in a page description language (hereinafter referred to as“PDL”), e.g., 8-bit image data in color channels consisting of fourcolors (C, M, Y, K) or three colors (R, G, B).

PDL refers to a language that is descriptive of image information,including format information, positional information, color information(including density information), etc., of characters, figures, etc., ina “page” that serves as an output unit for printing, displaying, or thelike. Known types of PDL include PDF (Portable Document Format accordingto IS032000-1:2008), PostScript (registered trademark) of Adobe SystemsIncorporated, and XPS (XML Paper Specification).

A color scanner, not shown, is connected to the editing apparatus 14.The color scanner is capable of optically reading a color original,which is set in position. Therefore, the editing apparatus 14 canacquire color image data in the form of an electronic manuscript fromthe color scanner based on the color original read thereby.

The image processing apparatus 16 converts the color image data of anelectronic manuscript described by PDL into bitmap image data (a type ofraster image data), and then performs a desired image processingprocess, e.g., a color conversion process, an image scaling process, animage arranging process, etc., on the bitmap image data, converts theprocessed bitmap image data into a print control signal that matches theprinting process of the printing machine 18, and sends the print controlsignal to the printing machine 18.

The image processing apparatus 16 comprises a main unit 22 including aCPU, a memory, etc., a display device 24 for displaying color images,and an input device 26 as an input unit including a keyboard 28 and amouse 30. A portable memory 32, which is capable of freely recording anderasing electronic data, and the colorimeter 20 are connected to theimage processing apparatus 16.

The printing machine 18 comprises an inkjet printing apparatus forproducing a color image based on a combination of standard inks ofcolors C, M, Y, K (process colors) and optional inks of light colorssuch as LC, LM, etc., and W (white). The printing machine 18 controlspropulsion of inks onto a print medium 34 (a rolled non-printed mediumas shown in FIG. 1) based on print control signals received from anexternal apparatus, e.g., the image processing apparatus 16, in order toprint a color image on the print medium 34, thereby producing a printedobject 36, which may include a color chart 36 c.

The print medium 34 may comprise a paper medium such as synthetic paper,thick paper, aluminum-evaporated paper or the like, a resin medium suchas vinyl chloride, PET or the like, or tarpaulin paper or the like.

The colorimeter 20 measures colorimetric values of an object to bemeasured. Colorimetric values refer not only to tristimulus values X, Y,Z, the coordinates L*, a*, b* of a uniform color space, etc., but alsoto a distribution of optical material characteristic values (hereinafterreferred to as “spectral data”) with respect to wavelengths, e.g., aspectral radiance distribution (spectral distribution), a spectralsensitivity distribution, spectral reflectance, or spectraltransmittance.

The printed object 36, which is obtained in this manner, is displayed ina location under a transmissive light source TS and a reflective lightsource RS, which serve as observational light sources.

FIG. 2 is a front elevational view of the color chart 36 c according tothe present embodiment.

The color chart 36 c shown in FIG. 2 comprises one hundred color patches38 of different colors, which are substantially identical in shape andarranged in rows and columns, a sequence of numbers 40 and a sequence ofalphabetical letters 42 for identifying positions of the color patches38 along directions of the rows and columns, and print information 44for identifying conditions for printing the color chart 36 c, all ofwhich is printed on the print medium 34.

The color patches 38 are arranged in a matrix having 10 vertical columnsand 10 horizontal rows, the vertical columns of the color patches 38being spaced from each other by given intervals. Colors of therespective color patches 38 are set to given values within a range ofsignal levels of C, M, Y, K values (a percentage range from 0% to 100%or an 8-bit gradation range from 0 to 255).

The sequence of numbers 40 represents a vertical string of charactersranging from (01) to (10) positioned in alignment with and to the leftof respective rows of color patches 38. The sequence of alphabeticalletters 42 represents a horizontal string of characters ranging from (A)to (J) positioned in alignment with and at the top of respective columnsof color patches 38.

The print information 44 is printed on the print medium 34 andrepresents the type and serial number, or a registered name of theprinting machine 18, a print mode (to be described later), the type ofprint medium 34, a print date, etc.

FIG. 3 is a functional block diagram of the image processing apparatus16 according to the present embodiment. In FIG. 3, an electronicmanuscript is supplied along directions indicated by the outlinedsolid-line arrows, image data for the color chart 36 c is supplied alongdirections indicated by the outlined broken-line arrows, and variousother data is supplied along directions indicated by the solid-linearrows.

As shown in FIG. 3, the main unit 22 of the image processing apparatus16 includes an I/F 46 for entering an electronic manuscript suppliedfrom the editing apparatus 14, a RIP (Raster Imaging Processor) 48 forconverting the PDL format of the electronic manuscript supplied from theI/F 46 into a raster format, a color converter 50 for performing a colorconversion process on the converted C, M, Y, K values (or R, G, Bvalues) of the electronic manuscript from the RIP 48 in order to produceimage data of new C, M, Y, K values, a printing machine driver 52 forconverting the image data of the new C, M, Y, K values produced by thecolor converter 50 into print control signals (ink propulsion controldata) that match the printing process of the printing machine 18, andanother I/F 54 for outputting the print control signals generated by theprinting machine driver 52 to the printing machine 18.

The main unit 22 also includes a color manager 56 for managing profilesfor different printing machines 18, an image data generator 58 forgenerating image data to print the color chart 36 c, an optical materialcharacteristic value-estimating unit 60 for estimating optical materialcharacteristic values of a later-mentioned laminate film, an I/F 62connected to the display device 24, an I/F 64 connected to the inputdevice 26 including the keyboard 28 and the mouse 30, an I/F 66connected to the colorimeter 20, and an I/F 68 connected to the portablememory 32.

The main unit 22 also includes a storage unit 70 for storing variousdata supplied from various components in the interior of the main unit22, and for supplying the stored data to various components of the mainunit 22. The storage unit 70 is connected to the RIP 48, the colorconverter 50, the color manager 56, the image data generator 58, theoptical material characteristic value-estimating unit 60, the I/F 62,the I/F 64, the I/F 66, and the I/F 68.

The color converter 50 comprises an input profile processor 72 forconverting device-dependent data into device-independent data, and anoutput profile processor 74 for converting device-independent data intodevice-dependent data. Device-dependent data refer to data defined interms of C, M, Y, K values, R, G, B values, or the like, forappropriately driving various devices. Device-independent data refer todata defined in terms of a display system, such as an HSV(Hue-Saturation-Value) system, an HLS (Hue-Lightness-Saturation) system,a CIELAB system, a CIELUV system, an X, Y, Z system, or the like.

The color manager 56 comprises an input profile generator 76 forgenerating input profiles for respective printing machines 18, and anoutput profile generator 78 (profile generator) for generating outputprofiles for respective printing machines 18.

The RIP 48 can perform various image processing processes, including animage scaling process depending on resolution, etc., of the printingmachine 18, and a rotating and inverting process depending on a printingformat utilized when an electronic manuscript is converted into a rasterformat.

From the C, M, Y, K values, the printing machine driver 52 generates inkpropulsion control data corresponding to ink colors (C, M, Y, K, LC, LM,or W). The ink propulsion control data are related to operationaldetails of the printing machine 18, which serve to eject the inks (inkejection ON/OFF, ink dot diameters, etc.) according to data definitionsinherent in the printing machine 18. In this process, the printingmachine driver 52 has to convert from an 8-bit multiple-gradation imageinto a low-gradation image such as a binary image to generate the inkpropulsion control data. For such a conversion, the printing machinedriver 52 may use a known algorithm, such as a dither matrix method, anerror diffusion method, or the like.

The input profile processor 72 or the output profile processor 74 iscapable of correcting a profile depending on a print mode of theprinting machine 18. The print mode refers to various print settings,such as the number of nozzles of the print head, the timing(unidirectional/bidirectional) of ink ejection during scanning of theprint head, the number of passes, the number and type of inks used inthe printing machine 18, and an algorithm for generating ink ejectioncontrol data, etc.

Furthermore, a controller (not shown) is provided, comprising a CPU,etc., for controlling all of the image processing processes describedabove. More specifically, the controller controls not only operation ofvarious components of the main unit 22 (e.g., reading data from andwriting data to the storage unit 70), but also transmission of displaysignals via the I/F 62 to the display device 24, and acquisition ofcolorimetric data from the colorimeter 20 via the I/F 66.

The image processing apparatus 16 according to the first embodiment isconstructed as described above. Image processing processes or otherfunctions described above can be performed according to applicationsoftware (programs), which are stored in the storage unit 70, and whichoperate under the control of a basic program (operating system).

The aforementioned program is recorded in a computer readable recordingmedium (for example, the portable memory 32 shown in FIG. 1). Theprogram, which is stored in the recording medium, may be read in andexecuted by a computer system. The term “computer system” as used hereinmay include an OS (operating system) or hardware embodied in peripheraldevices or the like. Such a computer readable medium may be a portablestorage device such as a flexible disk, magneto-optical disk, ROM,CD-ROM or the like, or a hard disk that is internal to the computersystem. The computer readable medium may hold programs dynamically andfor a short time period, as in the case of a transmission line, in whichprograms are transmitted to the computer over a communications circuitmade up of an internet network, a telephone circuit line, or the like,and may include holding of programs for a certain length of time, as inthe case of a volatile memory internal to a server/client type ofcomputer system.

FIG. 4 is a functional block diagram of the output profile generator 78according to the present embodiment.

The output profile generator 78 basically comprises a data selector 90,a colorimetric value calculator 92, and a LUT generator 94.

The data selector 90 selects spectral transmittance data of the medium34 under profile generating conditions (hereinafter referred to as“first spectral data 106”), based on setting data 96, and a group 98 ofspectral transmittance data of mediums, which are read out from thestorage unit 70. The data selector 90 selects spectral reflectance dataof the medium 34 under profile generating conditions (hereinafterreferred to as “second spectral data 108”), based on setting data 96,and a group 100 of spectral reflectance data of mediums, which are readout from the storage unit 70. The data selector 90 also selects spectralradiance distribution data of the transmissive light source TS underprofile generating conditions (hereinafter referred to as “thirdspectral data 110”), based on setting data 96, and a group 102 ofspectral radiance distribution data of transmissive light sources, whichare read out from the storage unit 70. The data selector 90 also selectsspectral radiance distribution data of the reflective light source RSunder profile generating conditions (hereinafter referred to as “fourthspectral data 112”), based on setting data 96, and a group 104 ofspectral radiance distribution data of reflective light sources, whichare read out from the storage unit 70. The setting data 96 are types ofmediums 34, transmissive light sources TS, and reflective light sourcesRS that are set by the operator and which relate to the profilegenerating conditions.

The colorimetric value calculator 92 calculates colorimetric value data116 under profile generating conditions, based on the first, second,third, and fourth spectral data 106, 108, 110, 112 selected by the dataselector 90, and degree of influence data 114, which expresses a rate ofcontribution of the transmissive light source TS and the reflectivelight source RS with respect to how the printed object 36 is viewed.

The LUT generator 94 generates a LUT 120 under profile generatingconditions based on the colorimetric value data 116 calculated by thecolorimetric value calculator 92, and C, M, Y, K value data 118corresponding to the respective color patches 38 (see FIG. 2).

In the present embodiment, spectral data are given respectively inassociation with one hundred color patches 38 whose patch numbers rangefrom 0 to 99. The light wavelengths have forty-one data λ₁ through λ₄₁associated therewith. For example, the light wavelengths are representedby λ₁=400 nm, . . . , λ₄₁=800 nm at intervals of 10 nm.

FIGS. 5A through 5D are views showing by way of example setting screensfor setting profile generating conditions according to the presentembodiment.

FIG. 5A shows a setting screen 130 having three pull-down menus 132,134, 136, a textbox 138, and buttons 140, 142 labeled “GENERATE” and“CANCEL”, respectively, arranged successively downward.

The setting screen 130 includes a string of letters indicating “MEDIUM”on the left side of the pull-down menu 132. When the operator operatesthe mouse 30 in a certain way, a selection column 144 also is displayedbeneath the pull-down menu 132, as shown in FIG. 5B, with a scroll bar146 added to the right side of the selection column 144.

The setting screen 130 includes a string of letters indicating“TRANSMISSIVE LIGHT SOURCE” on the left side of the pull-down menu 134.When the operator operates the mouse 30 in a certain way, a selectioncolumn 148 also is displayed beneath the pull-down menu 134, as shown inFIG. 5C, with a scroll bar 150 added to the right side of the selectioncolumn 148.

The setting screen 130 includes a string of letters indicating“REFLECTIVE LIGHT SOURCE” on the left side of the pull-down menu 136.When the operator operates the mouse 30 in a certain way, a selectioncolumn 152 also is displayed beneath the pull-down menu 136, as shown inFIG. 5D, with a scroll bar 154 added to the right side of the selectioncolumn 152.

The setting screen 130 includes a string of letters indicating “PROFILENAME” on the left side of the textbox 138. The operator can entercharacter information into the textbox 138 through operation of thekeyboard 28.

FIG. 6 is a view showing by way of example a setting screen for settingprofile generating conditions according to the present embodiment.

A setting screen 160 has an arrow symbol 162, a gauge 164, a slider 166,two textboxes 168, 170, and buttons 172, 174 labeled “DETERMINE” and“CANCEL”, respectively, arranged successively downward.

The arrow symbol 162 extends in right and left directions of the settingscreen 160, the lefthand side thereof indicating “transmissive light”,and the righthand side thereof indicating “reflective light”. The gauge164 also extends in right and left directions of the setting screen 160,and is provided with the slider 166, which is movable in left and rightdirections over the gauge 164.

Beneath the lefthand end of the gauge 164, the textbox 168 is providedin which numerical values can be entered, and in which, for example, thenumber “0.4” is displayed. Beneath the righthand end of the gauge 164,the textbox 170 is provided in which numerical values can be entered,and in which, for example, the number “0.6” is displayed.

The printing system 10 according to the present embodiment basically isconstructed as described above. Operations of the printing system 10will be described below.

FIG. 7 is a flowchart of a sequence for producing a printed object 36having appropriate colors, by using the printing system 10 according tothe present embodiment. A process for producing the printed object 36will be described below, mainly with reference to FIG. 1.

First, the operator examines printing conditions and observationalmanners of a printed object 36 to be produced (step S1). Such printingconditions refer to the type of printing machine 18 that is used toproduce the printed object 36, the type of print medium 34, and theprint mode referred to above, etc. Observational manners refer to aspectral radiation distribution of the transmissive light source TS orthe reflective light source RS, and the manner in which the printedobject 36 is displayed (reflection, transmission, or a combinationthereof).

Then, the operator selects a profile suitable for the printing machine18 (step S2). Normally, an input profile or an output profile is storedin the storage unit 70 of the main unit 22. If a profile suitable forthe printing machine 18 has not been registered, i.e., is not stored inthe storage unit 70, then an output profile can be generated separately.

Next, an electronic manuscript is printed using the printing machine 18,whereby a printed object 36 is obtained (step S3). A lamination processmay be carried out on the printed object 36 using a non-illustratedlaminating apparatus, whereby a protective film can be applied to animage-formed surface of the printed object 36. If this is done, theproduced printed object 36 has an increased level of abrasion resistanceand toughness.

Then, the operator evaluates the colors in the color image of theprinted object 36 (step S4), and determines whether or not the colors inthe color image are appropriate (step S5). The operator may evaluatecolors of the color image in order to determine whether desired hues areobtained, for example, either by visually checking the color image basedon observation of an overall or partial appearance of the color image,or by acquiring a colorimetric value of a certain area of the printedobject 36 with the colorimeter 20, and determining whether or not theobtained colorimetric value falls within a desired range.

If, as a result of such image evaluation, the operator judges that thecolor of the color image of the printed object 36 is not suitable, thenthe operator changes the profile in order to make fine adjustments tothe colors of the color image (step S6). More specifically, as detailedmethods therefor, the operator may reset or regenerate the profile, maymake fine adjustments to the profile (i.e., correct the presently setprofile), or may make corrections to the print data of the printedmanuscript.

Thereafter, an electronic manuscript is printed and colors of the colorimage itself are evaluated repeatedly (steps S3 through S6) until aprinted object 36 having desired colors is obtained.

An image processing sequence carried out by the image processingapparatus 16 for printing an electronic manuscript (step S3) will bedescribed in detail below with reference to FIG. 3.

When an electronic manuscript in PDL format supplied from the editingapparatus 14 is input to the image processing apparatus 16 via the LAN12 and the I/F 46, the electronic manuscript is converted into 8-bit C,M, Y, K raster data (device-dependent image data) by the RIP 48. Such8-bit C, M, Y, K raster data are then converted into X, Y, Z data(device-independent image data) by the input profile processor 72. SuchX, Y, Z data are then converted into C, M, Y, K value data(device-dependent image data) by the output profile processor 74. The C,M, Y, K value data are then converted into a print signal (ink ejectioncontrol data) by the printing machine driver 52. The print signal issupplied to the printing machine 18 from the printing machine driver 52via the I/F 54. Thereafter, the printing machine 18 produces a desiredprinted object 36 based on the print signal. Raster data, which isconverted by the RIP 48, may be stored temporarily in the storage unit70, as necessary.

Since input profiles and output profiles corresponding to a plurality ofset conditions have been stored in the storage unit 70, an input profileand an output profile are supplied selectively to the input profileprocessor 72 and the output profile processor 74, depending on variouspreset conditions. If such profiles are appropriately corrected in viewof the print mode of the printing machine 18, then more appropriatecolor conversion processes can be performed.

The flowchart shown in FIG. 7, for producing a printed object 36 havingappropriate colors with the printing system 10 according to the presentembodiment, has been described above. Next, a process for generating aprofile (step S2) will be described in detail below with reference tothe flowchart shown in FIG. 8.

First, the operator confirms whether or not there exists degree ofinfluence data 114 of the light source (step S21). If degree ofinfluence data 114 is not present, the degree of influence of the lightsource under observation is obtained (step S22). As stated previously,the degree of influence expresses a rate of contribution of thetransmissive light source TS and the reflective light source RS withrespect to how the printed object 36 is viewed. For example, among theradiant light from each of the light sources, a ratio of the lightintensity therefrom that actually reaches the retina of a human observervia the printed object 36 corresponds to such a “degree of influence”.

FIG. 9A is a perspective view for explaining a method used to measurethe luminance Lt of the transmissive light source TS under observation.First, an unprinted medium 34 is arranged in a display location, whichhas been determined beforehand, for the printed object 36. On the backsurface side of the unprinted medium 34, a flat diffusion plate 188 isaffixed tightly. The back surface is defined as a surface that isopposite from the observed surface (front surface) in the event that theimage is formed on the medium 34.

On the other hand, on the front surface side of the medium 34, aspectral emission luminosity meter 190 (second acquisition unit) isdisposed, such that the medium 34, the diffusion plate 188, and thetransmissive light source TS are arranged on the optical axis of thespectral emission luminosity meter 190. Further, the spectral emissionluminosity meter 190 is separated from the medium 34 by a given distanceat which it is assumed the printed object 36 will be observed (e.g., ata general observation distance of 350 mm).

Furthermore, in order to block completely radiant light that is emittedtoward the front surface side of the medium 34 from the reflective lightsource RS, a dark screen 192 is positioned so as to cover or shield thespectral emission luminosity meter 190 from the reflective light sourceRS.

Under such a positional relationship, the luminosity (cd/m²) of thefront surface side of the medium 34 is measured by the spectral emissionluminosity meter 190. When done in this manner, under a condition inwhich the effect of the reflective light source RS is removed, theelemental luminosity Lt of the transmissive light source TS alone can bemeasured.

FIG. 9B is a perspective view for explaining a method used to measurethe luminance Lr of the reflective light source RS under observation. Incomparison to FIG. 9A, the positional relationship by which the medium34, the diffusion plate 188, and the spectral emission luminosity meter190 are placed in alignment is the same.

On the other hand, compared to FIG. 9A, the arrangement shown in FIG. 9Bis different, in that the dark screen 192 has been removed, and thetransmissive light source TS is turned off so as not to emit light.

Under such a positional relationship, the luminosity (cd/m²) of thefront surface side of the medium 34 is measured by the spectral emissionluminosity meter 190. When done in this manner, under a condition inwhich the effect of the transmissive light source TS is removed, theelemental luminosity Lr of the reflective light source RS alone can bemeasured.

Thereafter, using the measured luminosities Lt and Lr, the degree ofinfluence thereof can be determined. As a simplest and highly precisecalculation method, as shown in equations (1) and (2) below, the degreeof influence Ct, Cr can be calculated using the relative ratio of eachluminosity.

Ct=Lt/(Lt+Lr)  (1)

Cr=Lr/(Lt+Lr)  (2)

As is self-evident from equations (1) and (2), because a relationship isestablished in which Ct+Cr=1, the values Ct and Cr are standardizedvalues. Hereinbelow, according to the present embodiment, the rates ofcontribution Ct, Cr of the transmissive light source TS and thereflective light source RS, respectively, are utilized as degree ofinfluence data 114.

After the degree of influence data 114 is acquired, the degree ofinfluence is set by means of the setting screen 160 shown in FIG. 6. Thenumerical values displayed in the textboxes 168, 170 indicate the degreeof influence Ct, Cr corresponding to the transmissive light source TSand the reflective light source RS, respectively.

For example, by a dragging operation of the mouse 30 (see FIG. 1), whenthe slider 166 is caused to move in left and right directions along thegauge 164, settings for the degree of influence are changed. At thistime, the degree of influence is determined corresponding to the stoppedposition of the slider 166 on the gauge 164, and numerical values aredisplayed in the textboxes 168, 170.

Similarly, by operating the keyboard 28 (see FIG. 1), predeterminednumerical values can be input into the textboxes 168, 170 to thereby setthe degree of influence.

Then the operator presses the “DETERMINE” button 172 disposed at thebottom of the setting screen 160. Upon doing so, the input values in thetextboxes 168, 170 are supplied to the main unit 22 as degree ofinfluence data 114, and the values are stored in the storage unit 70. Onthe other hand, when the “CANCEL” button 174 is pressed, the settingscreen closes and the setting operation is brought to an end.

In this manner, degree of influence data 114 of the light sources areset (step S23).

Next, the operator confirms whether or not the type of print medium 34used for printing has been registered (step S24).

If not yet registered, spectral data of the printed object 36, which isproduced by the print medium 34, is acquired (step S25). For example,the operator prepares the portable memory 32, which stores spectral data(spectral transmittance and spectral reflectance of the printed object36 produced by the print medium 34) therein, and connects the portablememory 32 to the main unit 22 of the image processing apparatus 16.Spectral data stored in the portable memory 32 are automatically ormanually transferred as new data to the storage unit 70. Alternatively,spectral data may be managed by the database DB (see FIG. 1) and, ifnecessary, acquired therefrom and transferred to the storage unit 70.

Further, alternatively, spectral data of the printed object 36 producedby the print medium 34 may be acquired directly using the colorimeter20, which is connected to the main unit 22. A process of directlyacquiring spectral data using the colorimeter 20 will be describedbelow, mainly with reference to FIG. 3.

The operator enters a request to print the color chart 36 c into asetting screen (not shown), which is displayed on the display device 24.In response to the request, the image data generator 58 of the main unit22 generates image data (C, M, Y, K values) for printing the color chart36 c, and supplies the generated image data to the printing machinedriver 52 from the path indicated by the outlined broken-line arrows.The printing machine driver 52 then converts the image data into a printsignal, which is supplied to the printing machine 18 in the same manneras when an electronic manuscript is printed. In this manner, the colorchart 36 c (see FIG. 2) is printed.

The C, M, Y, K value data 118 (see FIG. 4), which correspond to pixelsof the respective color patches 38, are stored in the storage unit 70 inadvance, and are read from the storage unit 70 when image data isgenerated.

Using the colorimeter 20, which is connected to the image processingapparatus 16, the operator measures the spectral transmittance and thespectral reflectance of each of the color patches 38 of the color chart36 c (see FIG. 2). Preferably, the colorimeter 20 used for making suchmeasurements is capable of measuring either one of spectraltransmittance or spectral reflectance, simply by switching themeasurement mode thereof.

Because the same color chart 36 c is measured twice, as shown in FIG. 2,the order in which color measurements are made for each of the colorpatches 38 preferably is set beforehand, as a sequence forcolorimetrically measuring the color patches 38, e.g., (01) through (10)on column (A) and (01) through (10) on column (B), using the numbers 40and alphabetical letters 42 shown in FIG. 2.

Based on a notification that the operator has completed the colorimetricmeasurement, the spectral data corresponding to the color patches 38 arestored in the storage unit 70 via the I/F 66, in relation to the type ofprint medium 34 (see FIG. 3).

After spectral data have been saved in the storage unit 70, a new typeof print medium 34 can be selected from the selection column 144 of thepull-down menu 132 shown in FIG. 5B. In FIG. 5B, “PVC A” (where “PVC”refers to polyvinyl chloride”) is selected.

The type of print medium 34 is thus established (step S26).

The operator then confirms whether or not the types of observationallight sources (transmissive light source TS and reflective light sourceRS) have been registered (step S27). If not yet registered, thenspectral data of the light sources are acquired (step S28). As notedabove, the portable memory 32 may store spectral data of the lightsources (i.e., spectral radiation distributions of the transmissivelight source TS and the reflective light source RS), and the operatormay acquire such spectral data from the portable memory 32.

After the spectral data have been stored, a new type of transmissivelight source TS can be selected from the selection column 148 of thepull-down menu 134 shown in FIG. 5C. In FIG. 5C, a light source “F8” isselected and set.

Further, a new type of reflective light source RS can be selected fromthe selection column 152 of the pull-down menu 136 shown in FIG. 5D. InFIG. 5D, a light source “A” is selected and set.

In this manner, types of observational light sources (transmissive lightsource TS and reflective light source

RS) are established (step S29).

Finally, profile generating conditions, made up of the degree ofinfluence Ct (=1−Cr) established in step S23, the type of print medium34 established in step S26, and the types of light sources, i.e., thetransmissive light source TS and the reflective light source RS,established in step S29 are saved (step S30).

After a profile name to be generated has been entered and registered inthe textbox 138 shown in FIG. 5A, the operator presses the “GENERATE”button 140. Various settings (setting data 96) are now input through theI/F 64 to the main unit 22, whereupon such data are stored automaticallyin the storage unit 70.

Thereafter, as shown in FIG. 4, the first, second, third and fourthspectral data 106, 108, 110, 112, which are associated with the settingdata 96, are selected by the data selector 90, from among the settingdata 96 supplied from the storage unit 70, the group 98 of spectraltransmittance data of print mediums, the group 100 of spectralreflectance data of print mediums, the group 102 of spectral radiationdistribution data of the transmissive light sources, and the group 104of spectral radiation distribution data of the reflective light sources.It goes without saying that the first spectral data 106 and the secondspectral data 108 should be selected as the same type of print medium34.

Then, the colorimetric value calculator 92 calculates colorimetric valuedata 116 under profile generating conditions, based on the first,second, third, and fourth spectral data 106, 108, 110, 112, along withthe degree of influence data 114.

The colorimetric value data 116 under profile generating conditions aretristimulus values X, Y, Z calculated based on actual measured data, fora case in which the printed object 36 is observed under an environmentwhere the transmissive light source TS and the reflective light sourceRS coexist.

Tristimulus values of the color patches 38 under the transmissive lightsource TS are defined by (Xt, Yt, Zt). The tristimulus values (Xt, Yt,Zt) correspond to values, which are produced by multiplying the spectralradiation distribution of the transmissive light source TS, the spectraltransmittance of the printed object 36, and a color matching function,and integrating the product within a range of visible wavelengths.

Tristimulus values of the color patches 38 under the reflective lightsource RS are defined by (Xr, Yr, Zr). The tristimulus values (Xr, Yr,Zr) correspond to values, which are produced by multiplying the spectralradiation distribution of the reflective light source RS, the spectraltransmittance of the printed object 36, and a color matching function,and integrating the product within a range of visible wavelengths.

The tristimulus values (X, Y, Z) of each of the color patches 38 undersuch a mixed lighting environment are calculated using the degree ofinfluence Ct according to the following equations (3) to (5):

X=Ct·Xt+(1−Ct)·Xr  (3)

Y=Ct·Yt+(1−Ct)·Yr  (4)

Z=Ct·Zt+(1−Ct)·Zr  (5)

According to the present embodiment, one hundred individual colorpatches 38 are measured respectively, so that one hundred sets of X, Y,Z values are obtained.

The LUT generator 94 generates the lookup table LUT 120 for convertingthe three-dimensional output profile data (X, Y, Z) intofour-dimensional data (C, M, Y, K), based on an association between theone hundred sets of colorimetric value data 116 (X, Y, Z) and onehundred sets of C, M, Y, K value data 118.

With the above arrangement, output profiles corresponding to each ofprofile generating conditions are stored beforehand in the storage unit70, so that when a print request for an electronic manuscript is made, astructure is adopted in which the output profiles are read outselectively corresponding to setting conditions. Accordingly, it isunnecessary to regenerate output profiles that have already beengenerated once, and thus the computational time required for imageprocessing can be shortened.

Alternatively, a configuration may also be adopted in which, each timethat a printing request for an electronic manuscript is made, an outputprofile is generated corresponding to the setting conditions for theprint, and the output profile is supplied to the color converter 50. Ifdone in this manner, the amount of data stored in the storage unit 70can be reduced.

In the above manner, as indicated by step S2 in FIG. 7, profiles for theprinting machine 18 can be generated. In particular, color reproductionaccuracy can be further enhanced as a result of generating profileswhile taking into consideration the following three points.

-   1. Prediction of Spectral Reflectance of Printed Object After Being    Covered with a Protective Film

In the case that a laminate film 200 (see FIG. 10) is applied as aprotective layer to an image-formed surface of the printed object 36,the appearance of the color image changes to such a degree that itcannot be ignored, depending on the presence or absence of such alaminate film 200. Below, a printed object that is formed in this mannershall be referred to as a “protective-film-covered print”.

In the case that strict color reproduction is to be carried out withrespect to such a protective-film-covered print, printing of a colorchart 36 c with respect to the total combination of the printed object36 and the laminate film 200, a lamination process, and colorimetricmeasurements thereof must all be performed, thus posing a troublesomeburden.

On the other hand, the spectral transmittance of aprotective-film-covered print can be predicted comparatively easily andwith high precision according to a so-called multiplicative rule forspectral transmittance, i.e., by multiplying together the spectraltransmittance of the printed object 36 and the spectral transmittance ofthe laminate film 200.

However, for spectral reflectance, because there are cases in which asimilar type of multiplicative rule cannot be established, the spectralreflectance of the protective-film-covered print cannot easily bepredicted. Thus, it is desirable to accurately predict the spectralreflectance of the protective-film-covered print using a knownKubelka-Munk theoretical model.

More specifically, based on the following equation (6), the spectralreflectance R of the protective-film-covered print is predicted.Although it is understood that each of the variables is a function ofoptical wavelength, for purposes of simplification, explanations of suchfunctions, which are well known in the art, have been omitted.

R=[(R _(g) −R _(∞))/R _(∞) −R _(∞)(R _(g)−1/R _(∞))exp{Sx(1/R _(∞) −R_(∞))}]/[(R _(g) −R _(∞))−(R _(g)−1/R _(∞))exp{Sx(1/R _(∞) −R_(∞))}]  (6)

In the above equation (6), “R_(g)” represents the spectral reflectance(second spectral data 108) of the printed object 36 alone, “R_(∞)”represents the specific spectral reflectance of the laminate film 200,“S” represents a scattering coefficient per unit thickness of thelaminate film 200, and “x” represents the actual thickness of thelaminate film 200.

Next, a method shall be explained in detail for estimatingexperimentally the unknown variables for R_(∞) (specific reflectance)and Sx (scattering coefficient), which are optical physical values ofthe laminate film 200.

FIG. 10 is an outline view in cross section of a measurement specimen194, made for the purpose of estimating optical material property valuesof the laminate film 200.

The measurement specimen 194 comprises a substrate 196 having a spectralreflectance of Rg₁ made up from a white non-transparent body, a blackmaterial 198, and the laminate film 200, which serves as an object to bemeasured.

An operator, using the colorimeter 20, measures the spectral reflectanceof each location on the measurement specimen 194. As a result,measurement values are obtained of the spectral reflectance R₁ when thelaminate film 200 is applied to cover the substrate 196, the spectralreflectance Rg₂ when the black material 198 is disposed on the substrate196, and the spectral reflectance R₂ (R₁>R₂) when the substrate 196 iscovered by the laminate film 200 with the black material 198 interveningtherebetween.

These measurement values are stored initially in the storage unit 70 viathe I/F 66 provided in the main unit 22 of the image processingapparatus 16. Thereafter, the measurement values are supplied to theoptical material characteristic value-estimating unit 60, in which acomputational process is carried out according to the followingequations (7) and (8).

The specific reflectance R_(∞) of the laminate film 200 is calculated bymathematical analysis, as follows:

R _(∞)={C−√(C ²−4)}/2  (7)

where

C={(R ₁ +Rg ₂) (R ₂ ·Rg ₁−1)−(R ₂ +Rg ₁) (R ₁ ·Rg ₂−1)}/(R ₂ ·Rg ₁ −R ₁·Rg ₂)  (8)

In the case that R₁<R₂, the subscripts 1 and 2 in the above equation (8)are reversed. The specific reflectance R_(∞) is a reflectance for a casein which it is assumed that the thickness of the test specimen isunlimited.

Next, using the actual measured value R_(n) (n=1 or 2), the actualmeasured value Rg_(n) (n=1 or 2), and R_(∞) as calculated by equation(5), the scattering coefficient S and the thickness x of the laminatefilm 200 are calculated as follows by equation (9),

S·x=ln[{(R _(∞) −Rg _(n)) (1/R _(∞) −R _(n))}/{(R _(∞) −R _(n)) (1/R_(∞) −Rg _(n))}]/(1/R _(∞) −R _(∞))  (9)

where S is the scattering coefficient per unit thickness, and x is theactual thickness of the laminate film 200. Concerning the definition ofthe scattering coefficient, although for purposes of simplification Sx(=S·x) has been defined as a scattering coefficient (i.e., as onevariable) at a given film thickness x, either S or Sx may be used.Further, the same holds true as well for the absorption coefficient K.

Moreover, the following relationship, shown by equation (10), existsbetween the specific reflectance R_(∞), the scattering coefficient S,and the absorption coefficient K.

K/S=(1−R _(∞))²/2R _(∞)  (10)

Therefore, the absorption coefficient K (or Kx) may be used instead ofeither the specific reflectance R_(∞) or the scattering coefficient S(or Sx). In other words, from among these three optical materialcharacteristic values, once any two of them has been determined, thevalue of the other one can be determined uniquely.

Furthermore, using the compensation formula of Saunderson, and so on,the Kubelka-Munk model may be applied on the basis of a compensatedvalue of the actually measured spectral reflectance R_(n). See,“Calculation of the Color of Pigmented Plastics”, JOURNAL OF THE OPTICALSOCIETY OF AMERICA, volume 32, pp. 727-736 (1942). By means of suchcompensation, light reflection at the interface between the laminatefilm 200 and the exterior is taken into consideration, so that thespectral reflectance of the protective-film-covered print can bepredicted with even greater accuracy.

In the foregoing manner, using the optical material characteristicvalues of the laminate film 200, the spectral transmittance and spectralreflectance of a protective-film-covered print can be predicted withgood accuracy.

-   2. Color Conversion Processing Based on Consideration of Changes in    Spectral Sensitivity Distribution

Color conversion in accordance with a normal ICC profile is premised oncolor matching performed under a standard light source (D50).Accordingly, while referring to an average spectral sensitivitydistribution of an observer under a D50 light source, a color matchingfunction is determined, and tristimulus values X, Y, Z are calculatedbased on the determined color matching function.

However, because the spectral sensitivity distribution of the observerchanges corresponding to the surrounding environmental light, as aresult, even if the main light source is the same, a phenomenon (socalled color adaptation) occurs such that the appearance of the colorstends to change. In particular, with a transmissive image in a darklocation and a reflective image in a bright location, because thedifference in the surrounding environmental light is large, there is afear that suitable color matching cannot be realized. Thus, it isdesirable for color conversion processing to be carried out while takinginto consideration such changes in spectral sensitivity.

FIG. 11 is a detailed functional block diagram of a color converter 50in which changes in spectral sensitivity distribution are taken intoconsideration. Each of the labels “A”, “D50”, and “F8” shown on the leftand right edges of the drawing indicates attributes of the spectralsensitivity distribution (color matching function) corresponding to eachof image data on which the various types of conversion processing areimplemented.

C, M, Y, K value data 202 are converted into L*, a*, value data 204 bythe input profile processor 72. The L*, a*, b* value data then areconverted into C, M, Y, K value data 206 by the output profile processor74. Below, an explanation shall be made for a case in which the C, M, Y,K value data 202 under an A light source, and the C, M, Y, K value data206 under an F8 light source make up appropriate image data.

First, the C, M, Y, K (CMYK) value data 202 are converted once into X,Y, Z (XYZ) value data corresponding to the light source D50 by a CMYK toXYZ converter 208. As stated above, color conversion according to an ICCprofile is premised on color matching performed under a D50 lightsource.

Next, by means of a color adaptation converter 210, the X, Y, Z valuedata corresponding to the light source D50 are converted into X, Y, Zvalue data corresponding to the light source A. Such color adaptationconversion can be performed using various conversion models. Forexample, Von-Kries conversion may be used, or a color adaptation matrix,which is stored in the profile, may be used.

Next, X, Y, Z (XYZ) value data corresponding to the light source A areconverted into the L*, a*, b* (L*a*b*) value data 204 by an XYZ toL*a*b* converter 212. Such L*, a*, b* value data 204 are data in a colorperception space that does not depend on the device or the observationallight source. For example, a CIECAM97s or a CIECAM02 model may be usedto produce such data.

Next, the L*, a*, b* value data 204 are converted into X, Y, Z valuedata corresponding to the light source F8 by an L*a*b* to XYZ converter214, and further, by means of a color adaptation converter 216, the X,Y, Z value data corresponding to the light source F8 are converted onceinto X, Y, Z value data corresponding to the light source D50, inaccordance with the same reasoning as discussed previously.

Lastly, X, Y, Z (XYZ) value data corresponding to the light source D50are converted into C, M, Y, K (CMYK) value data 206 by an XYZ to CMYKconverter 218. Such C, M, Y, K value data 206 define C, M, Y, K valuedata for obtaining a printed object 36 that exhibits appropriate colors,for a case in which printing is performed by the printing machine 18 andthe printed object 36 is observed under an F8 light source.

In the foregoing manner, color conversion processing can be carried outwhile taking into consideration changes in the spectral sensitivitydistribution, so that appropriate color matching can be realized even incases where the surrounding environmental lights are different (e.g., atransmissive image in a dark location and a reflective image in a brightlocation).

-   3. Print Color Predictive Simulation Using Color Calibration    Apparatus

As one example for determining the degree of influence of thetransmissive light source TS and the reflective light source RS, therewas disclosed above the method for measuring respectively the luminanceLt and the luminance Lr of the transmissive light source TS and thereflective light source RS (see FIGS. 9A and 9B). However, there may becases in which measurement data of the luminance Lt and the luminance Lrare not available, or in which further fine adjustments are desirablewith respect to an obtained degree of influence Ct.

Consequently, a print color calibration system 300 can be constructed,in which, without using the printing machine 18, the way in which colorsof the printed object 36 are viewed is predicted when observed in anenvironment where both a transmissive light source TS and a reflectivelight source RS coexist, and an appropriate degree of influence of thelight sources is determined.

FIG. 12 is a perspective explanatory view of a print color calibrationsystem 300 in which a high function monitor 304 is incorporated as acolor calibration device according to the present embodiment.

The print color calibration system 300 is constituted by a processingsystem or PC 302 equipped with imaging processing functions, and thehigh function monitor 304 that serves as a color calibration device.

The processing system 302 is connected to the LAN 12, so as to beconnected mutually wirelessly or over wires with the image processingapparatus 16. The high function monitor 304 includes high definitiondisplay capabilities, such as high luminosity, a wide range gamut, and ahigh contrast ratio, etc., which are capable of reproducingsubstantially the gamut of the printing machine 18.

The processing system 302 comprises an I/F 306 to which an electronicmanuscript supplied from the image processing apparatus 16 is input, acolor converter 308 (including as sub-elements thereof an input profileprocessor 310 and an output profile processor 312), which implements apredetermined color conversion process with respect to the Y, M, C, Kvalue data of the electronic manuscript supplied via the I/F 306 inorder to acquire new R, G, B value image data, a monitor driver 314 forconverting the new R, G, B value image data, which have been colorconverted and acquired from the color converter 308, to display controlsignals suitable for the high function monitor 304, and an I/F 316 fortransmitting the display control signals converted by the monitor driver314 to the high function monitor 304.

Further, the processing system 302 is equipped with a storage unit 318for storing an input profile and an output profile. The storage unit 318supplies the input profile to the input profile processor 310, and alsosupplies the output profile to the output profile processor 312.

As shall be explained below, as a result of being constructed in theforegoing manner, a print color predictive simulation can be carried outusing the high function monitor 304.

Image data converted by the output profile processor 74 shown in FIG. 3(i.e., image data immediately before being supplied to the printingmachine driver 52) is transmitted externally of the image processingapparatus 16 via a non-illustrated I/F. At this time, the print profileof the printing machine 18 is transmitted simultaneously therewith. Suchdata is supplied to the processing system 302 via the I/F 306 shown inFIG. 12.

Once the print profile for the printing machine 18 has been stored inthe storage unit 318, and thereafter, an input profile and an outputprofile are supplied to the color converter 308. In the color converter308, the print profile for the printing machine 18 is supplied to theinput profile processor 310, whereas a display profile for the highfunction monitor 304 is supplied to the output profile processor 312.

On the other hand, C, M, Y, K raster format image data supplied via theI/F 306 are converted by the input profile processor 310 into L*, a*, b*coordinates, which then are converted by the output profile processor312 into R, G, B values, and converted by the monitor driver 314 intodisplay control signals, which are supplied to the high function monitor304 via the I/F 316. Thereafter, the high function monitor 304 displaysa desired reference image.

The operator confirms visually the color shading or hues of thereference image displayed on the high function monitor 304. When it isjudged that the hues of the reference image are not suitable, theoperator slides to the left or right the slider 166 of the settingscreen 160 (see FIG. 6), which may be displayed on the display device 24or on the high function monitor 304, thereby changing the value of thedegree of influence data 114 (see FIG. 4).

In accordance with such a change in value, the print profile of theprinting machine 18 and the image data (i.e., the image data immediatelybefore being supplied to the printing machine driver 52) are changed,and a reference image is displayed rapidly on the high function monitor304 in the same manner as discussed previously.

When performed in this manner, the operator can make fine adjustments tothe degree of influence, while confirming visually the color shading orhues of the reference image. More specifically, using the high functionmonitor 304 serving as a color calibration apparatus, a predictivesimulation of the print colors is carried out, so that an optimal degreeof influence can be estimated. Since the reference image can beconfirmed without requiring a printed object 36 to be obtained each timethe degree of influence is changed, the print color calibration system300 is both effective and economical.

Although a preferred embodiment of the present invention has been shownand described in detail, the invention is not limited by thisembodiment, and various changes and modifications may be made theretowithout departing from the scope of the invention as set forth in theappended claims.

For example, in the present embodiment, the color chart 36 c has onehundred color patches 38, there are forty-one spectral data, and thelight wavelengths are spaced at intervals of 10 nm. However, thesenumerical values may be changed freely, considering comprehensivelyfeatures such as color reproduction accuracy, image processing time,etc.

Further, in the present embodiment, the printing machine 18 comprises aninkjet printing apparatus. However, the printing machine 18 is notlimited to any particular type of apparatus, and the advantages andeffects of the invention can be obtained with an electrophotographicapparatus, a thermosensitive apparatus, or the like.

What is claimed is:
 1. A colorimetric value calculating method forcalculating a colorimetric value of a printed object including an imageformed on a light-transmissive medium in an observational environment inwhich both a transmissive light source and a reflective light sourcecoexist, comprising: a first acquisition step for acquiring a spectraltransmittance of the printed object and a spectral reflectance of theprinted object; a second acquisition step for acquiring a spectraldistribution of the transmissive light source and a spectraldistribution of the reflective light source; and a calculating step forcalculating the colorimetric value of the printed object in theobservational environment, using the obtained spectral transmittance ofthe printed object, the obtained spectral reflectance of the printedobject, the obtained spectral distribution of the transmissive lightsource, and the obtained spectral distribution of the reflective lightsource.
 2. A colorimetric value calculating method according to claim 1,further comprising a third acquisition step for acquiring a degree ofinfluence of the transmissive light source and the reflective lightsource with respect to how the printed object is viewed, wherein thecalculating step calculates the colorimetric value of the printed objectin the observational environment further using the degree of influence.3. A colorimetric value calculating method according to claim 1, furthercomprising: an estimating step of estimating an optical materialcharacteristic value of a protective film; a third acquiring step ofacquiring a spectral transmittance of the protective film; a firstpredicting step of predicting a spectral transmittance of aprotective-film-covered print, which is made up of the printed objectcovered by the protective film, using the spectral transmittance of theprinted object and the obtained spectral transmittance of the protectivefilm; and a second predicting step of predicting a spectral reflectanceof the protective-film-covered print, using a spectral reflectance ofthe printed object and the estimated optical material characteristicvalue of the protective film, wherein the calculating step calculates acolorimetric value of the protective-film-covered print in theobservational environment.
 4. A colorimetric value calculating methodaccording to claim 1, wherein the first acquisition step is performedusing a measuring unit for measuring the light sources or an acquiringunit for acquiring data from a database.
 5. A colorimetric valuecalculating method according to claim 2, wherein the third acquisitionstep is performed using an acquiring unit for acquiring the degree ofinfluence based on a setting by a user, or using an acquiring unit foracquiring the degree of influence by measuring the transmissive lightsource and the reflective light source.
 6. A colorimetric valuecalculating method according to claim 2, further comprising: anestimating step of estimating an optical material characteristic valueof a protective film; a fourth acquiring step of acquiring a spectraltransmittance of the protective film; a first predicting step ofpredicting a spectral transmittance of a protective-film-covered print,which is made up of the printed object covered by the protective film,using the spectral transmittance of the printed object and the obtainedspectral transmittance of the protective film; and a second predictingstep of predicting a spectral reflectance of the protective-film-coveredprint, using a spectral reflectance of the printed object and theestimated optical material characteristic value of the protective film,wherein the calculating step calculates a colorimetric value of theprotective-film-covered print in the observational environment.
 7. Aprofile generating method comprising: a first acquisition step ofacquiring a spectral transmittance and a spectral reflectance of a colorchart serving as a printed object formed on a light-transmissive medium;a second acquisition step for acquiring a spectral distribution of atransmissive light source and a spectral distribution of a reflectivelight source, which act as observational light sources for the printedobject; a calculating step for calculating a colorimetric value of thecolor chart in an observational environment in which the transmissivelight source and the reflective light source coexist, using the obtainedspectral transmittance of the color chart, the obtained spectralreflectance of the color chart, the obtained spectral distribution ofthe transmissive light source, and the obtained spectral distribution ofthe reflective light source; and a generating step of generating a printprofile based on the calculated colorimetric value of the color chart.8. A color conversion method comprising: a first acquisition step ofacquiring a spectral transmittance and a spectral reflectance of a colorchart serving as a printed object formed on a light-transmissive medium;a second acquisition step for acquiring a spectral distribution of atransmissive light source and a spectral distribution of a reflectivelight source, which act as observational light sources for the printedobject; a calculating step for calculating a colorimetric value of thecolor chart in an observational environment in which the transmissivelight source and the reflective light source coexist, using the obtainedspectral transmittance of the color chart, the obtained spectralreflectance of the color chart, the obtained spectral distribution ofthe transmissive light source, and the obtained spectral distribution ofthe reflective light source; a generating step of generating a printprofile based on the calculated colorimetric value of the color chart;and a color converting step of color converting image data showing animage to be printed, while using an arbitrary profile as an inputprofile and using the generated print profile as an output profile.
 9. Acolor conversion method according to claim 8, further comprising: aninput step of further color converting the color converted image dataand supplying the same to a color calibration apparatus, while using theprint profile as an input profile and using a profile of the colorcalibration apparatus as an output profile; and an adjusting step ofadjusting a degree of influence of the transmissive light source and thereflective light source with respect to how the printed object isviewed, while referring to the image output from the color calibrationapparatus.
 10. A color conversion apparatus for performing colorconversion on a printed object including an image formed on alight-transmissive medium in an observational environment in which botha transmissive light source and a reflective light source coexist,comprising: a first acquisition unit for acquiring a spectraltransmittance of the printed object and a spectral reflectance of theprinted object; a second acquisition unit for acquiring a spectraldistribution of the transmissive light source and a spectraldistribution of the reflective light source; a calculating unit forcalculating a colorimetric value of the printed object in theobservational environment, using the spectral transmittance of theprinted object and the spectral reflectance of the printed objectobtained from the first acquisition unit, together with the spectraldistribution of the transmissive light source and the spectraldistribution of the reflective light source obtained from the secondacquisition unit; a profile generating unit for generating a printprofile based on the colorimetric value of the printed object in theobservational environment as calculated by the calculating unit; and acolor converter for color converting image data showing the image to beprinted, while using an arbitrary profile as an input profile, and usingthe print profile generated by the profile generating unit as an outputprofile.
 11. A computer-readable recording medium recording therein acolor conversion program for enabling a computer to carry out colorconversion on a printed object including an image formed on alight-transmissive medium in an observational environment in which botha transmissive light source and a reflective light source coexist, theprogram further enabling the computer to function as: means foracquiring a spectral transmittance of the printed object and a spectralreflectance of the printed object; means for acquiring a spectraldistribution of the transmissive light source and a spectraldistribution of the reflective light source; means for calculating acolorimetric value of the printed object in the observationalenvironment, using the spectral transmittance of the printed object, thespectral reflectance of the printed object, the spectral distribution ofthe transmissive light source, and the spectral distribution of thereflective light source; means for generating a print profile based onthe calculated colorimetric value of the printed object in theobservational environment; and means for color converting image datashowing the image to be printed, while using an arbitrary profile as aninput profile, and using the generated print profile as an outputprofile.